Generally, plural component products which require isolation of their components during storage have such a requirement because of chemical reactions which occur upon mixing the components. A familiar example of such a two component product which must have its components isolated from each other during storage is epoxy adhesive comprising resin and hardener components. The resin and hardener must be stored independently because, upon being mixed, a chemical reaction occurs which causes hardening or setting of the adhesive. Successive batches of resin and hardener are desirable dispensed and mixed in predetermined proportions to achieve uniform, predictable product properties from batch-to-batch.
The prior art discloses a broad variety of collapsible co-dispensing tubular container constructions. See for instance French Pat. No. 961,154, published May 8, 1950 titled "Improvement in Tubes For Ointments Or The Like"; German Pat. No. 580,134, filed July 17, 1931; U.S. Pat. No. 3,290,422, issued Dec. 6, 1966 to Kenneth George Michel; U.S. Pat. No. 3,506,157 issued Apr. 14, 1970 to Joseph Dukess; and, U.S. Pat. No. 3,307,738 issued Mar. 7, 1967 to Christian Theodore Scheindel. Moreover, other co-dispensing tube constructions are disclosed in the co-pending commonly assigned U.S. patent application Ser. No. 601,688 filed Aug. 1, 1975 by Charles R. Hood and Stephen F. Evans titled "Collapsible Longitudinally Partitioned Tubular Dispensing Container", which application is a continuation of now abandoned U.S. patent application Ser. No. 415,468, filed Nov. 13, 1973, both of which applications are hereby incorporated by reference.
A long felt problem associated with collapsible co-dispensing tubular containers has been variations in the ratio of dispensing the two product components. That is, when such containers are operated intermittently (e.g., a toothpaste tube used by a variety of family members throughout the course of a day), variations in grip, squeezing pressure, and the like precipitate variations in the ratio of the product components being co-dispensed. The present invention comprises means near the head end of the container for equalizing the pressures on the two product components so that, at least with respect to product components of substantially equal viscosities, substantially constant proportionation of the co-dispensed components occurs. That is, the two components are caused to be expressed at uniform rates by virtue of being expressed under equal pressures and by virture of having substantially equal viscosities. None of the referenced prior art has solved all of the problems associated with providing constant proportionation from collapsible co-dispensing tubular containers in the manner of nor to the degree of the present invention.